Spring crop pests mild, but growers should scout for summer insects

Spring crop pests mild, but growers should scout for summer insects

By Hannah Harper | Posted on 7/10/2013

Adult western corn rootworm. (Purdue Entomology/John Obermeyer)

WEST LAFAYETTE, Ind. - Mild temperatures and moderate rainfall during corn and soybean planting created prime conditions for avoiding severe problems with spring pests, a Purdue Extension entomologist says. But that doesn't mean growers should let their guard down when it comes to summer insects.

Indiana's two largest cash crops have not been affected by as many spring insects as in past years, partly because of the lack of extreme temperatures and rainfall once planting got underway.

"The lack of spring insects is mostly a factor of the crops getting planted into conditions that were virtually ideal - soils were mostly moist but not wet at planting, and we did not have extended cool and rainy conditions," Christian Krupke said.

Cool, wet spring weather can delay planting, causing the emergence of spring larvae to coincide with emerging crops. Under these conditions, spring feeders reach the later larval stage - when most feeding occurs - as crops begin to grow. This can hurt developing crops by stunting or stopping growth as these insects use the plants as a primary food source.

But while spring insects have not had a large presence in Indiana fields, Krupke said farmers still need to be out scouting their crops for summer insects.

"As we reach midsummer, ear feeders and root worms, as well as soybean aphids might come on the scene," he said.

Common summer-feeding insects in Indiana corn include western corn rootworms and western bean cutworm in northern parts of the state. At high infestation levels, both can cause major yield reductions, but recent years have seen very low populations.

Soybean aphids, one of Indiana's most common and serious summer soybean pests, attacks the crop until September and can reduce yields by 10-15 percent, but again no problems of this magnitude have been seen in at least four years.